A light field encompasses all the light rays at every point in space traveling in every direction. Light fields are considered four dimensional because every point in a three-dimensional space also has an associated direction, which is the fourth dimension.
Wearable three-dimensional displays may include a substrate guided optical device, also known as the light-guide optical element (LOE) system. Such devices are manufactured by, for example Lumus Ltd. However, these LOE systems only project a single depth plane, focused at infinity, with a spherical wave front curvature of zero.
One prior art system (Lumus) comprises multiple angle-dependent reflectors embedded in a waveguide to outcouple light from the face of the waveguide. Another prior art system (BAE) embeds a linear diffraction grating within the waveguide to change the angle of incident light propagating along the waveguide. By changing the angle of light beyond the threshold of TIR, the light escapes from one or more lateral faces of the waveguide. The linear diffraction grating has a low diffraction efficiency, so only a fraction of the light energy is directed out of the waveguide, each time the light encounters the linear diffraction grating. By outcoupling the light at multiple locations along the grating, the exit pupil of the display system is effectively increased.
A primary limitation of the prior art systems is that they only relay collimated images to the eyes (i.e., images at optical infinity). Collimated displays are adequate for many applications in avionics, where pilots are frequently focused upon very distant objects (e.g., distant terrain or other aircraft). However, for many other head-up or augmented reality applications, it is desirable to allow users to focus their eyes upon (i.e., “accommodate” to) objects closer than optical infinity.
The wearable 3D displays may be used for so called “virtual reality” or “augmented reality” experiences, wherein digitally reproduced images or portions thereof are presented to a user in a manner wherein they seem to be, or may be perceived as, real. A virtual reality, or “VR”, scenario typically involves presentation of digital or virtual image information without transparency to other actual real-world visual input; an augmented reality, or “AR”, scenario typically involves presentation of digital or virtual image information as an augmentation to visualization of the actual world around the user.
The U.S. patent applications listed above present systems and techniques to work with the visual configuration of a typical human to address various challenges in virtual reality and augmented reality applications. The design of these virtual reality and/or augmented reality systems (AR systems) presents numerous challenges, including the speed of the system in delivering virtual content, quality of virtual content, eye relief of the user, size and portability of the system, and other system and optical challenges.
The systems and techniques described herein are configured to work with the visual configuration of the typical human to address these challenges.